The Flow Cytometry Core will provide essential expertise, support and reagents to program project investigators for quantitative and phenotypic analysis of complex lymphocyte and antigen-presenting cell populations. In addition, considerable expertise is available for the design and implementation of high- throughput cell sorting experiments. The Core director Dr. Aguila, currently Associate Director of the Flow Cytometry Facility at UCHC, trained at Stanford in stem cell isolation by flow cytometry and so is well-versed at analysis and cell sorting of rare populations. The Flow Cytometry Facility is also well-equipped to handle the complexity as well as the volume of samples generated in this Program, having 6 analyzers and two high-speed cell sorters with multicolor capabilities. The equipment includes three BD-LSR 1 machines with two able to perform up to 15-parameter analysis and the third a five laser modified machine to allow up to 21 parameter analysis incuding multiple lines for detection of quantum dot-type reagents. Two five laser FACSAria lis are available for high-speed multicolor sorting and analysis. One of these is housed in a Baker hood to allow sorting of potentially infected tissues from mice or humans. In addition to support for facility costs, the Core will also provide technical assistance for processing, cell sorting, and analyzing samples and data. Having a dedicated research assistant for the Program will ensure uniformity of quality and help to increase efficiency and productivity. For these reasons the Flow Cytometry Core continues to be an integral component of each project and is therefore requisite to the success of this Program.